Panasonic KX-TDA0174, Service Manual, Page: 25 / 76

8.11. SELF-DIAGNOSIS
A self-diagnosis relay (RL201A) is installed in A port. In the normal operation mode, it breaks
the self-diagnosis relay, and in the self-diagnosis mode, it makes the self-diagnosis relay. In the
self-diagnostic mode, A Tip-Ring is connected to the paired Tip-Ring of the outside-line card via
backboard, and self-diagnosis is feasible.The self-diagnosis of the outside-line card includes
outside call pick up, dial pulse transmission, DTMF transmission, BELL reception and CPC
detection.
8.12. POWER FAILURE SWITCH FEATURE
4 out of 16 lines have switching relays (RL200A-D) installed in order to enable the outside call
during a power failure. The line connected to the outside call card will be directly connected to
he CN201/202 located in forward part of the board via a 4-conductor TEL cord. In the normal
operation mode, it breaks the power failure switching relay, and during a power failure, it makes
the power failure switching relay to initiate Power failure direct connection mode.
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